1. Field of the Invention
This invention relates to an apparatus for securing a rigid plate and, in particular, to a multiple actuator latch used to secure a circuit board.
2. Description of the Related Art
System flexibility is a highly desirable trait which allows a system to respond to the changing needs and/or requirements of a user or group of users. One solution to the need for flexibility is the incorporation of interchangeable parts within such systems. This is especially true in electronics applications, where interchangability of parts increases the lifespan and functionality of a system. Interchangeable parts may be switched, upgraded, or removed without having to replace the entire system. One such interchangeable part often used in computer-based applications is the printed circuit board (PCB). Computer systems may be fabricated to use a plurality of PCBs, each containing a portion of the electronics required to allow the computer system to operate.
To address the need for interchangeability in complex electronics applications, e.g. computer systems, "card racks" (or "card cages") have been developed. A card rack is a relatively large enclosure containing racks or shelves capable of holding a number of PCBs in a parallel configuration. A typical card rack 500 holding a number of PCBs 501 is shown in FIG. 8. Card rack 500 consists of side plates 502 and 503 connected by supports 504. A backplane 505 is connected to side plates 502 and 503 and includes electrical connectors 506, at least one connector 506 being provided for each of the PCBs 501. Connectors 506 releasably engage connectors 507 on the PCBs 501 to allow communication between the PCB 501 and the system of which card rack 500 is a portion. Plug 508 is inserted through aperture 509 into engagement with pin connectors to complete the physical installation of the PCBs 501.
Card racks and PCB's are found in numerous telecommunications applications, e.g. line units and trunk units. PCBs 501 for telecommunications applications may be in the form of circuit packs 516, as shown in FIG. 9. Each circuit pack 516 includes a plurality of signal processing components 518 mounted on a planar surface 520 of a rigid plate 522. The rigid plate 522 includes conductive paths 524 for interconnecting the components 518 to one another and to connector 507. Connector 507 is mounted on the rigid plate 522, generally on an end face of the rigid plate 522. The connector 507 contains pins and/or sockets for mating with matching connectors fixedly mounted on a rear wall of a card rack. Circuit pack 516, a specific type of PCB 501, may be removably mounted in a side-by-side, parallel relationship within a card rack 500 relative to other PCBs 501 and side plates 502, 503, as shown in FIG. 8.
The circuit pack 516 has a front face plate 528 which is mounted to the rigid plate 522. Mounting and dismounting of the circuit pack 516 occurs by sliding the edges of the rigid plate 522 along grooves within support walls of the card rack 500. Latches 530 are provided on the face plate 528 or rigid plate 522 to allow the circuit pack 516 to be secured to the card rack 500.
A known latch 530 is shown in FIG. 10. The latch 530 consists of a body portion 532; a handle portion 534 comprising both an actuating member 536 and a stop portion 538; a locking portion 540; a hooked portion 542; and a pivot point 544 which is used to pivotally mount latch 530 to rigid plate 522. The portion 545 of latch 530 nearest the rigid plate 522 is split into two sections to a depth defined by dotted line 547 which allows latch 530 to straddle the edge 549 of rigid plate 522. In operation, the latch 530 is pivoted about a pin 546 and pivot point 544 until locking portion 540 contacts an inside surface of card rack 500. The latch 530 is secured by applying downward pressure, e.g. through an operator's finger, in direction 550 to actuator 536 which allows hooked portion 542 to be raised above pin 548. While retaining downward pressure in direction 550, additional pressure is placed on the actuator 536 in direction 552 until hooked portion 542 passes over pin 548. The pressure on actuator 536 is then released, e.g. by the operator removing the finger, allowing hooked portion 542 to be lowered and engage pin 548. To release the latch 530, downward pressure is again applied to actuator 536 which raises hooked portion 542 and allows the latch 530 to become disengaged from pin 548 and rotate freely in the reverse of direction 552.
Latches 530 of the type shown in FIG. 10 are susceptible to inadvertent or accidental removal of the rigid plate 522. A single motion on the actuator 536 may cause the latch 530 to become disengaged and allow the circuit pack 516 to be removed. In addition, if an actuator 530 becomes weakened or loose (e.g. from use, environmental conditions, etc.) the latch 530 may become disengaged. Such a result is not only undesirable, but may result in large-scale system failure if an essential circuit pack 516 is inadvertently removed.
Thus, there exists a need for a securing mechanism for a circuit board which prevents accidental or inadvertent removal of the board once it is inserted and connected into a card rack.